[PATCH] drm/sched: test before reading fence timestamp

[Yunxiang Li]

Reading fence timestamp always need to check the corresponding flag bit
before to make sure the write is actually visible, otherwise we can read
garbage here.

Fixes: 1774baa64f93 ("drm/scheduler: Change scheduled fence track v2")
Signed-off-by: Yunxiang Li <yunxiang...@amd.com>
---
 drivers/gpu/drm/scheduler/sched_main.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/scheduler/sched_main.c 
b/drivers/gpu/drm/scheduler/sched_main.c
index 506371c42745..8ed00f54c59d 100644
--- a/drivers/gpu/drm/scheduler/sched_main.c
+++ b/drivers/gpu/drm/scheduler/sched_main.c
@@ -928,6 +928,9 @@ drm_sched_get_cleanup_job(struct drm_gpu_scheduler *sched)
                                                typeof(*next), list);
 
                if (next) {
+                       while (!test_bit(DMA_FENCE_FLAG_TIMESTAMP_BIT,
+                                        &job->s_fence->finished.flags))
+                               cpu_relax();
                        next->s_fence->scheduled.timestamp =
                                job->s_fence->finished.timestamp;
                        /* start TO timer for next job */
-- 
2.34.1